Abstract
Resolving the origin of endangered taxa is an essential component of conservation. This information can be used to guide efforts of bolstering genetic diversity, and also enables species recovery and future evolutionary studies. Here, we used low-coverage whole genome sequencing to clarify the origin of Helianthus schweinitzii, an endangered tetraploid sunflower that is endemic to the Piedmont Plateau in the eastern United States. We surveyed four accessions representing four populations of H. schweinitzii and 38 accessions of six purported parental species. Using de novo approaches, we assembled 87,004 bp of the chloroplast genome and 6770 bp of the nuclear 35S rDNA. Phylogenetic reconstructions based on the chloroplast genome revealed no reciprocal monophyly of taxa. In contrast, nuclear rDNA data strongly supported the currently accepted sections of the genus Helianthus. Information from combined cpDNA and rDNA provided evidence that H. schweinitzii is likely an allo-tetraploid that formed as a result of hybridization between the diploids Helianthus giganteus and Helianthus microcephalus.
Highlights
Since the implementation of screens for allozyme variation [1,2] and through recent developments in generation sequencing [3], molecular data have provided conservation managers and evolutionary biologists with key information for conservation planning
Phylogenetic analyses based on a chloroplast DNA alignment of 87,004 bp did not recover any perennial sunflower species as reciprocally monophyletic
While the branches were not monophyletic, there were some associations between H. angustifolius, H. simulans and H. floridanus of the Angustifolii series
Summary
Since the implementation of screens for allozyme variation [1,2] and through recent developments in generation sequencing [3], molecular data have provided conservation managers and evolutionary biologists with key information for conservation planning. This information has been used, for example, to designate evolutionarily significant units for conservation action by augmenting knowledge on the morphology and ecology of populations [4,5]. Constructive effects include the reversal of inbreeding depression following from restricted population sizes [9], or the enhancement of adaptive potential [10]
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